1. Field of the Invention.
The present invention relates to the field of angioplasty. In particular, the present invention relates to a dilatation balloon catheter.
2. Description of the Prior Art.
Angioplasty has gained wide acceptance in recent years as an efficient and effective method for treating types of vascular diseases. In particular, angioplasty is widely used for opening stenoses in the coronary arteries, although it is also used for treatment of stenoses in other parts of the vascular system.
The most widely used form of angioplasty makes use of a dilatation catheter which has an inflatable balloon at its distal end. Using fluoroscopy, the physician guides the catheter through the vascular system until the balloon is positioned across the stenosis. The balloon is then inflated by supplying fluid under pressure through an inflation lumen to the balloon. The inflation of the balloon causes stretching of the artery and pressing of the lesion into the artery wall to re-establish acceptable blood flow through the artery.
In order to treat very tight stenoses with small openings, there has been a continuing effort to reduce the profile of the catheter so that the catheter cannot only reach but also cross such a very tight stenosis.
In addition, a percutaneous transluminal coronary angioplasty (PTCA) system has been developed by applicant's assignee which makes use of a very low profile balloon catheter or "dilating guide wire" over which a second dilatation catheter can pass. The smaller dialating guide wire is first moved across a very tight stenosis, and the balloon of the dilating guide wire is inflated to partially open the stenosis. Subsequently, the larger diameter dilatation cathether is advanced over the dilating guide wire and across the stenosis. The balloon of the larger diameter catheter is then inflated to open further the stenosis.
The need to decrease dilatation catheter profiles has, however, brought with it certain practical limitations. In particular, the ability to transmit torque from the proximal to the distal end of the guide wire (or the catheter) in order to steer its distal tip through the vascular system and across a stenosis has been compromised. The need to reduce profile can compromise purgeability using conventional vacuum techniques. Therefore, there is a continuing need for improved torque response and tip control along with continued efforts for reduction in catheter profile, while facilitating a positive pressure purge.